Voice messaging systems, such as answering machines and the like, allow a caller to leave a message for a called party who is unavailable. Typically, a message prerecorded on a voice messaging system invites a caller to provide a telephone number to which a return call can be directed. Too often, callers who are concerned about their loss of privacy face the dilemma of choosing between their desire for a return call from the called party, and their reluctance to divulge their personal phone number to the called party (and/or all other potential listeners of the message recorded on the voice messaging system). For example, when a physician calls a patient from his home, the physician may not want to "publicize" his home phone number in a recorded (or non-recorded) message when the patient is unavailable. Security reasons may also prevent a caller from leaving his or her phone number in a message, notwithstanding the caller's great desire to be called back by the unavailable called party.
Unfortunately, callers' actions (or lack thereof) to protect their privacy, such as their refusal to leave a message, are sometimes defeated by factors that are independent of their will. For example, when an answering machine is coupled to a caller identification display unit (referred to as "caller-id display" for short) that records and displays originating telephone numbers for incoming calls, the caller's refusal to leave a message is unavailing. In response to this problem, a particular standard has been included in the Integrated Services Digital Network (ISDN) set of standards to allow callers to mark their telephone number as "Private Presentation Restricted" for their outgoing calls. Implementation of that particular ISDN standard effectively prevents called parties from receiving telephone numbers associated with incoming calls. Unfortunately, broad public acceptance of ISDN-based products and services has been slower than anticipated due to their relatively high cost compared to Plain Old Telephone Service (POTS) or POTS-based end-user telecommunications devices. As a result, the standard for preventing the display of originating telephone numbers on a per-call basis has not been widely implemented. Thus, a problem of the prior art is lack of a simple and cost-effective mechanism that allows callers with POTS lines (or ISDN lines) to protect their privacy without restraining their use of communications services.